Scientists believe there is a vast network of tunnels beneath the lunar surface. Volcanic structures, known as ‘Lava tunnels’, have previously been proposed as potential sites to establish human colonies at the moon. According to a study that was presented at the Conference of Lunar and Planetary Science, 1 km “lava tubes” could be stable enough to hold permanent underground bases. This would also help protect future colonizers of hostilities of the environment, extreme temperature, impacts of meteorites, and cosmic radiation, etc…
“Lava tubes are tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, said Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences who is involved in the research.” Source
Because of the low gravity, it is expected that the tunnels of the Moon are greater than those that exist on our planet. And while so far we have not found any concrete example of them, lunar probes have photographed cave entrances that could continue well under the surface of Earth’s moon.
“This wouldn’t be possible on Earth, but gravity is much lower on the moon and lunar rock doesn’t have to withstand the same weathering and erosion,” David Blair reported. “In theory, huge lava tubes — big enough to easily house a city — could be structurally sound on the moon.”
Using existing data, David Blair and his colleagues at Purdue University in West Lafayette, used computer models to determine the stability of the lunar lava tubes. After testing with different sizes, shapes and thicknesses of ceilings, they concluded that tunnels with a diameter of over 1 km have the stability to be habitable and protect its inhabitants from hazardous conditions.
“There has been some discussion of whether lava tubes might exist on the moon,” Jay Melosh said in a Purdue press statement. “Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big.”
David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon.
“We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the moon,” Blair said. “This wouldn’t be possible on Earth, but gravity is much lower on the moon and lunar rock doesn’t have to withstand the same weathering and erosion. In theory, huge lava tubes – big enough to easily house a city – could be structurally sound on the moon.”